The mechanical properties of a welded surface formed under “dry” welding conditions is frequently recorded to be greater than or equal to 23% elongation of tensile allweld. This stands in marked contrast to the mechanical properties of a welded surface which is formed under “wet” welding conditions. The elongation of tensile allweld for an underwater welded surface is typically about 7–8% due to rapid cooling of the welded surface through heat dispersion to the surrounding water and a high concentration of hydrogen absorbed into the weld. The underwater welded surface is thus more brittle and weaker than a weld formed on a surface made of the same material under “dry” conditions.
It is known to provide large hyperbaric chambers which are constructed around, so as to fully enclose, an underwater surface which requires welding. Such hyperbaric chambers are large enough to hold a diver and the diver's welding apparatus. In use, the hyperbaric chamber is drained of water and the diver welds the surface under “dry” conditions. The procedure is lengthy, and costly. The hyperbaric chambers are large and cumbersome to operate, and they are frequently oversized for the surface area which requires welding. Not surprisingly, the hyperbaric chambers are very expensive. For a very small welded area, the cost can run into many millions of dollars.
The present invention seeks to overcome at least some of the aforementioned disadvantages.